Interpretive Summary: This manuscript reviews current knowledge concerning nutritional effects on immune response, respiratory disease, and metabolic disorders of cattle fed in feedyards. The diet cattle receive before, during and after the stress of marketing and transport to commercial feedyards can have a significant effect on animal immune response, the incidence and severity of respiratory ydisease, and the cost of production. For optimal production efficience, receiving diets should contain approximately 60 to 70% concentrate and 13 to 14% crude protein. Dietary supplementation with vitamin E also seems to reduce the incidence of respiratory disease, however, injections of vitamin E tend to increase disease incidence. In cattle fed high-concentrate feedlot diets, metabolic disorders such as bloat and acidosis can occur. Proper dietary management and supplementation with some ionophores can decrease these metabolic disorders.

Technical Abstract:
Health and nutrition and their interactions are critical components of productivity in animals. Another importantly interacting component is stress. Losses from morbidity and mortality associated with bovine respiratory disease and digestive disorders are of significant economic concern to the feedlot industry. Sound nutritional management can preempt or minimize the adverse effects of stress. Acidosis and bloat are the major digestive disorders in feedlot cattle. Ionophores, particularly monensin, have been used as a management tool to modulate feed intake and control digestive disturbances.